Pickling bath and inhibitor therefor



252. COMPOSITIONS, 4 1 51 Patented Feb. 17, 1931 UNITED STATES PATENT OFFICE EDWIN C. WRIGHT, F ELLWOOD CITY, PENNSYLVANIA, ASSIGNOB TO NATIONAL TUBE COMPANY A CORPORATION OF NEW JERSEY PICKLING BATH AND INHIBITOR THEREFOR tno Drawing. Application filed June 19, 1929. Serial No. 372,213.

This invention relates to pickling baths for cleaning the surface of steel plates, sheets, I wire, or tubes, of oxids or other impurities, and more particularly to inhibitors for such 6 baths to prevent the acid contained therein from attacking and deteriorating the metal beneath the surface to be cleaned.

An object of the invention is to provide a pickling bath having a relatively small quan- 10 tity of an inhibitor and to provide an inhibitor of great power and efliciency.

In my present invention, I form a pickling bath containing a dilute acid and a small quantity of the constituents, or the derivatives of the constituents of a coal tar fraction within a boiling point range of 270 centigrade to 350 centigrade. This fraction normally contains anthracene and other bydrocarbons. The active ingredients of the inhibitor are, however, the constituents of this fraction other than anthracene.

In forming a pickling bath with dilute sulfuric acid, which is the acid commonly employed for such bath, the coal tar constituents that are to be used as the inhibitor are sulphonated prior to the addition of the inhibitor to the bath.

As a. specific example of a bath embodying the present invention, one and one-half gal- 80 lons of coal tar having an initial boilirg point of 270 centigrade and an end boiling point of 350 centigrade is mixed with three gallons of concentrated sulfuric acid of a specific gravity of 66 Baum, and the mixture allowed to react for twenty-four hours. This chemical reaction transforms the coal tar fraction into a sulphonated product which iscorgpletel soluble in the pickling bath and serves to'di use the sulphonated product uniformly throughout the bath. The resulting sulphonated product is then mixed with three thousand gallons of a five percent. sulfuric acid solution. Theresulting bath using the coal tar fraction as described above reduces the amount of sulfuric acid consumed in pickling, the amount thus consumed being less than with any commercial inhibitor heretofore used. Only one addition of the coal tar product is required during the life of the bath. The

action of the inhibitor is moreover very effective, there being substantially no pitting gt ghe steel when subjected to the pickling What I claim is:

1. A pickling bath comprising a five per cent. solution of sulfuric acid and the sul; honated product oicoal tar distillates fihin a li o ling range oif 270 'centigrade ta" 3'5C0'ent igrade, other "than "anthracpii'oil 14 of said coal tar distillate to "about two thousand parts of said dilute acid.

2. A pickling bath comprising a dilute solution of sulfuric acid containing less than one per cent. of its weight of a sulphonated derivative of a coal tar distillate boiling within 270 centigrade to 350 centigrade, other than anthracene oil (C H In testimony whereof I have hereunto set m hand.

y EDWIN C. WRIGHT.

H in the pfo ortion ofabout one part 

